This invention relates to a Rigid Nonmetallic Conduit fitting specifically one, which attaches the pipe to the top of a watt-hour meter enclosure or other raintight enclosure.
The use a flange like connector for electoral pipe to prohibit the introduction of water, dust or fumes into an electrical enclosure has long been recognized. U.S. Pat. No. 1,382,741 to Pierson (1921), U.S. Pat. No. 2,862,040 to Curran (1958) and U.S. Pat. No. 3,910,608 to Phillips, Jr. (1975) are good examples of how this system was used in the past. Furthermore U.S. Pat. No. 2,651,008 to Johansson (1953), U.S. Pat. No. 3,628,097 to Kobryner (1971), U.S. Pat. No. 2,972,656 to Fisher (1961) and U.S. Pat. No. 3,238,422 also to Fisher (1966) teach the use of such “detachable” flanges in connection with watt-hour meter enclosures.
To date these flanges, known in the industry as “Meter Hubs” (or simply “Hubs” when used in connection with other raintight enclosures such as panel boxes and disconnects), have been made of metal and had a female threaded hole which could be screwed onto a rigid metallic conduit or a “Raintight” connector (suitable for the type wiring method used). The enclosures they are used with commonly have a circular protrusion at the top through which the conductors enter the box and threaded protrusions for the mounting screws. The before mentioned hubs contain corresponding recesses which create a “flashing effect” to prohibit the introduction of water thus making the enclosure “raintight”.
These “Meter Hubs” most often contain an inner ring that acts like a bushing to keep the conductors away from the sharp edges of the sheet metal enclosure. However, this ring often contains sharp burs left over from the casting process, which pose a hazard to the insulation of the conductors themselves. It is a common practice in the field by some of the better craftsman (but definitely not all) to debur the “Meter Hub” before installation.
The present method of connecting a rigid nonmetallic conduit (commonly known as PVC) to a watt-hour meter enclosure (or other rain-tight enclosure) is to glue the pipe into a male adapter that has been threaded into a “Meter Hub” that is attached to a watt-hour meter enclosure by the mounting screws. The inconsistencies due to manufacturing and the common practice of “drawing” the semi-flexible pipe to the wall with a strap, instead of bending a proper offset in the conduit, can cause a possible leak hazard in the male adapter.
There is a rigid nonmetallic meter hub available from some manufactures. Scepter® (a division of IPEX) part number MHU35 (product code 077965) is an example of this fitting. However, this fitting utilizes a similar “female type connection” to the conduit as does the male adapter in the above mentioned installation and is therefore susceptible to the same possible leak hazard.
“Male end” connectors have been available from many manufacturers and are known as “Box Adapters”. An example of this type of fitting would be Scepter® (a division of IPEX) Part number JBA35 (product code 077726). However, this fitting is not intended as a rain-tight fitting, simply a standard connection to an enclosure.
Another common type of flange, found in the electrical industry, that looks very similar to the invention, is used to attach a post light head to a wooden post such as the Pier Base by the Adjusta Post Company (Model # 249). These flanges are made of metal and are manufactured for a different purpose therefore do not have the recesses necessary to conform to a “raintight” enclosure.